The objective of this study is to determine whether any biochemical change in the cellular metabolism of chemical carcinogens occurs in an organism as it ages, and if so, whether these changes can be correlated with an increased vulnerability to cancer. This study will focus on the effect of age on the metabolism of aflatoxin B1 by liver. Using rats ranging in age from four to thirty months, the ability of homogenates of liver to convert aflatoxin B1 to its less carcinogenic metabolites will be determined using high pressure liquid chromatography. In addition, the activation of aflatoxin B1 by liver homogenates will be measured by the formation of aflatoxin-DNA adducts with exogenous DNA and the formation of mutagenic compounds in the Ames test. The ability of hepatocytes isolated from four- to thirty-month-old rats to metabolize and activate aflatoxin B1 will be studied. Using suspensions of hepatocytes, it will be possible to measure the effect of age on the formation of aflatoxin adducts with cellular macromolecules. The formation of aflatoxin adducts with liver macromolecules also will be compared as a function of age in vivo. Because DNA is assumed to be the macromolecular target in the induction of cancer by chemical carcinogens, special attention will be given throughout the study on the effect of age on the formation of aflatoxin-DNA adducts. In addition to quantifying the amount of aflatoxin-DNA formed, the aflatoxin-DNA adducts will be isolated and will be characterized by high pressure liquid chromatography. From this research, it will be possible to critically evaluate the effect of the aging process on the metabolism and activation of aflatoxin B1 by liver.